<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
        /* div {
        height: 500px;
      } */
        /* .box {
        overflow: hidden;
      } */
        /* .container {
        padding: 0 300px 0 200px;
        border: 1px solid black;
      } */
        
        html,
        body {
            height: 100%;
        }
        
        div {
            height: 100%;
        }
        
        .container {
            display: flex;
        }
        
        .content {
            flex: 1 1;
            order: 2;
            background: #f00;
        }
        
        .left {
            flex: 0 0 200px;
            background: #0f0;
        }
        
        .right {
            flex: 1 1;
            background: #00f;
        }
    </style>
</head>

<body>
    <div class="container">
        <div class="left">你好</div>
        <div class="right">我好</div>
    </div>
</body>

</html>